GM stated on the IDL that it will be available later because that is when they are going to be switching to Summit White on the Impalas too. They want to be able to paint only one white at the Oshawa plant. That is what Cheryl said on the IDL.

I missed that part of the IDL on the reasoning but mdkyss response is logical. The 2009 Malibu is now the 50U Summit White (changed from the 40U White) so it does stand to reason a July date would coincide with the changeover to 2010 production for the Impala at Oshawa and thus the Camaro available in White also.